New role for the protein tyrosine phosphatase DEP-1 in Akt activation and endothelial cell survival.
Functional inactivation of the protein tyrosine phosphatase DEP-1 leads to increased endothelial cell proliferation and failure of vessels to remodel and branch. DEP-1 has also been proposed to contribute to the contact inhibition of endothelial cell growth via dephosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2), a mediator of vascular development. However, how DEP-1 regulates VEGF-dependent signaling and biological responses remains ill-defined. We show here that DEP-1 targets tyrosine residues in the VEGFR2 kinase activation loop. Consequently, depletion of DEP-1 results in the increased phosphorylation of all major VEGFR2 autophosphorylation sites, but surprisingly, not in the overall stimulation of VEGF-dependent signaling. The increased phosphorylation of Src on Y529 under these conditions results in impaired Src and Akt activation. This inhibition is similarly observed upon expression of catalytically inactive DEP-1, and coexpression of an active Src-Y529F mutant rescues Akt activation. Reduced Src activity correlates with decreased phosphorylation of Gab1, an adapter protein involved in VEGF-dependent Akt activation. Hypophosphorylated Gab1 is unable to fully associate with phosphatidylinositol 3-kinase, VEGFR2, and VE-cadherin complexes, leading to suboptimal Akt activation and increased cell death. Overall, our results reveal that despite its negative role on global VEGFR2 phosphorylation, DEP-1 is a positive regulator of VEGF-mediated Src and Akt activation and endothelial cell survival.
Chabot
Catherine
C
CRCHUM-Centre Hospitalier de l'Université de Montréal and Institut du Cancer de Montréal, Montréal, Québec, Canada H2L 4M1.
Spring
Kathleen
K
Gratton
Jean-Philippe
JP
Elchebly
Mounib
M
Royal
Isabelle
I
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D017433:Protein Structure, Secondary; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013379:Substrate Specificity / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000737:chemistry / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C098587:GAB1 protein, human; D042461:Vascular Endothelial Growth Factor A; D019000:Phosphotyrosine; D019869:Phosphatidylinositol 3-Kinases; D040301:Vascular Endothelial Growth Factor Receptor-2; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt; C486288:PTPRJ protein, human; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3